IMO, there has to be a breach of the lease or the notice before you can file for eviction.

In my property that essentially has tree logs holding it up, there was later added some bracketing to secure the vertical log to the horizontal beam.

Definition I found online - A due-on-sale clause is a clause in a loan or promissory note that stipulates that the full balance of the loan may be called due (repaid in full) upon sale or transfer of ownership of the property used to secure the note.

My real estate goal is to become a successful real estate investor in order to secure my future.

We have class A/B houses that appeal to those with security clearances and other professional incomes.

I also have more than enough reserves to comfortably stash 8 months of expenses aside in the event of vacancies.Since my investor is an older gentleman and looking to secure himself some passive income for a while, part of our private mortgage deal was that I can't refinance before 10 years, but also that I must refinance before 15 years.  

If you don't you've effectively reduced the security deposit you hold by $300.

(I learned this 'cash for keys' just recently on BP) To me, it seems a straighforward breach of contract. 

As for the sub tenant if she has breached her contract you can have her evicted but court costs are no fun. 

Tenants should always have "skin in the game" namely the security deposit.